Bacteriostatic acrylonitrile polymers



United States Patent No Drawing. Filed Mar. 16, 1962, Ser. No. 188,349 6 (llaims. (Cl. 26t45.95)

This invention relates to bacteriostatic compositions of polyacrylonitrile or of copolymers containing at least 85 weight percent of acrylonitrile in the polymer molecule, and minor but elfective amounts of certain polychlorinated phenols, and to articles made from such compositions.

Polyacrylonitrile and many of the fiber and film-forming copolymers of acrylonitrile may advantageously be fabricated by a Wet spinning process wherein the polymer composition is extruded from compositions of the polymer in polyacrylonitrile-dissolving aqueous saline solvents, particularly aqueous solutions of zinc chloride and its saline equivalents. Such a procedure, as is well known in the art, is oftentimes referred to as salt-spinning with the fibers (or other shaped articles) obtained thereby being salt-spun. In salt-spinning, the fiber-forming, aqueous saline spinning solution or other composition of the polymer is extruded during the spinning operation into a non-polymer dissolving coagulation liquid or spin bath, which frequently is a solution of the same salt or salts as are in the spinning solution.

Acrylonitrile polymers (including fiber-forming copolyrisers), particularly polyacrylonitrile, :thiit are salt-spun in the referred-to manner are generally formed initially an 'aquagel intermediates. Such intermediates have a water-swollen or hydrated structure prior to their being finally irreversibly dried to the desired characteristically hydrophobic, product.

Advantageously, the aquagel structure of polyacrylonitrile and other fiber and film-forming acrylonitrile polymers may be derived by the extrusion of a solution of the acrylonitrile polymer that is dissolved in an aqueous zinc chloride saline solvent therefor into and coagulation in an aqueous coagulating spin bath. It is usually desirable for zinc chloride to be at least the principal (if not the entire) saline solute in the aqueous saline solvent solution.

If preferred, however, various of the saline equivalents for zinc chloride may also be employed in the aqueous saline solvent medium for the spinning solution and the coagulating bath utilized. These zinc chloride equivalents, as is well known, include various of the thiocyanates, (such as calcium thiocyanate), lithium bromide and the salts and salt mixtures that are solvent members of the so-called lyotropic series as are disclosed, among other places, in US. 2,140,921; 2,425,192; 7

2,648,592; 2,648,593; 2,648,646; 2,648,648; and 2,648, 649.

Fibers produced from acrylonitrile polymers have excellent physical properties but do not have the inherent ability to inhibit the growth of bacteria. The textile industry is particularly interested in a fibrous material useful for the production of blankets, carpeting and the like, which has the desirable properties of polyacrylonitrile tor fiber-forming copolymers containing at least 85 weight percent of acrylonitrile in the polymer molecule and in addition has the ability to inhibit the growth of bacteria and to destroy existing basteria. It is also highly desirable to prepare heat-shrinkable, flexible films useful for bottle closures and the like applications which have long-lasting bacteriostatic properties.

Fabricated acrylonitrile polymer films, textile fibers and like filamentous articles derived from salt-spinning Patented Aug. 3, i955 7 than about 0.1 inch, said articles being characterized by having orientation of the molecules parallel to one another and to a major axis of the article.

The foregoing statement of the problem has referred to fibers and films, and the invention will be illustrated with respect to fibers. The problem is more general, however, and applied to the defined compositions in the forms of sheets, tubes, rods and molded articles as well as films, fibers and other filaments.

It is the primary object of this invention to provide compositions of matter containing at least 85 weight percent of acrylonitrile in the polymer molecule which have long-lasting bacteriostatic properties.

A further object is to provide shaped articles from the compositions of the invention which have long-lasting bacteriostatic properties.

Other and related objects will become evident from the following specifications and claims.

These objects are realized, according to the invention, by dispersing within the fiber-forming acrylonitrile polymers defined herein at least about 0.5 weight percent and preferably from about 0.5 to 20 weight percent based on the weight of the fiber-forming polymer of a polychlorinated phenol having at least four chlorine atoms on the benzene nucleus asthe only substituents.

Articles made from the resulting compositions show pronounced bacteri taticgroperties even"after prolonged treatmer'it'with aheated aqueous detergent system.

According to a preferred embodiment of the present invention, a polymer containing at least 85 percent acrylonitrile in the polymer molecule, as described herein, is spun from an aqueous saline solution thereof into an aqueous coagulant. The coagulated product is stretched to efiect orientation and is washed in any conventional manner to extract saline constituents and is finally irreversibly dried. The polychlorinated phenol useful for the present invention, can be incorporated .in the spun article during the course of its manufacture or after it is reduced to its final dimensions and irreversibly dried.

The invention is applicable to products made by dryspinrung or wet-spinning from organic solutions of the polymer, as well as wet-spinning of aqueous saline solutions of the polymer.

The acrylonitrile polymer employed in practice of the present invention is advantageously, polyacrylonitrile, al though, as is readily apparent, any of the well known fiber and film-forming copolymers thereof that contain, polymerized in the polymer molecule, at least 85 weight percent of acrylonitrile with at least one other ethylenically unsaturated monomer that is copolymerizable with acrylonitrile may, beneficially, be utilized. The acrylonitrile polymer employed is soluble in an aqueous saline solvent which, usually, has therein at least about -60 weight percent of zinc chloride or its saline equivalents. US. 2,776,946, among many other reference sources, exemplifies many of the monomers which may be copolymerized or interpolymerized with acrylonitrile to produce binary or ternary acrylonitrile copolymers that are useful in the practice of the invention.

The polychlorinated phenols hereafter called bacteriostatic agents which are useful for the purposes of the present invention are readily available materials which contain four or more chlorine atoms on the benzene nucleus as the only substituents.

Specific bacteriostatic agents useful for the present invention include 2,3,4,6-tetrachlorophenol, pentachlorophenol and their alkali metal salts.

The bacteriostatic agent must be present in the shaped article in amounts of at least about 0.5 percent by weight, preferably 0.5 to 20 percent by weight, based on the weight of the polymer. The permissible maximum proportion depends on the limit of its compatibility with the organic spinning solution or aqueous saline solution, as well as the polymeric material contained therein. The maximum limit is generally about 20 weight percent, based on the weight of the acrylonitrile polymer.

The bacteriostatic agent can be added to the acrylonitrile polymer spinning solution in a mutual solvent therefor, or by milling said bacteriostatic agent to finely divided particles which are suspended in a small amount of the spinning solution media to form a concentrate thereof, followed by addition of said concentrate to the spinning solution with stirring.

Alternatively, the bacteriostatic agent can be incorporated into the water-swollen aquagel or finally oriented, irreversibly dried article by soaking the article in an aqueous solution of the bacteriostatic agent.

The time required for the aquagel or irreversibly dried article to absorb the bacteriostatic agent is very brief," and varies with the concentration of the liquid from which the bacteriostatic agent is applied, and the temperature of the application. Generally, enough of the bacteriostatic agent defined herein, is absorbed by the aquagel or irreversibly dried article in about 5 minutes or less. No adverse eifect is found when the polymeric article is soaked in the aqueous bacteriostatic solution for periods fof several days.

The bacteriostatic agent useful for the purposes of the present invention may be used in aqueous solutions which about 0.5 weight percent of the bacteriostatic agent, based on the weight of the fiber-forming polymer.

Amounts as high as 20 percent are unobjectionable. The temperature of treatment may be any temperature at which the aqueous bacteriostatic solution is a liquid, 'however, it is convenient to effect the treatment at temperatures of about 95 C.

It will be appreciated by those skilled in the art that various other additives and finishing agents commonly employed in the fiber and filament arts can be added to the compositions of the present invention. Such materials include, for example, plasictizers, lubricants, dye assistants, dyes and pigments.

' The following example, wherein all parts and percentages are to be taken by weight, illustrates the present invention but is not to be construed as limiting its scope.

Example 1 In each of a series of experiments, separate lengths (4 inches) of a water-swollen, unstretched tow, formed by extrusion of an aqueous saline solution of polyacrylonitrile through a mil, 300 hole metal spinneret into an aqueous coagulating bath, were washed thoroughly to remove salt, and were individually placed in each of a series of bottles separately containing 10 milliliters of a 1.0 percent aqueous solution of 2,3,4,6-tetrachlorophenol or pentachlorophenol, said bacteriostatic agents being in the form of their sodium salt. The solutions were each maintained at 96 C. for a period of about 10 minutes, until the fibers had absorbed the sodium salt of the bacteriostatic agent in amounts sufficient to provide at least about 0.5 weight percent of the corresponding bacteriostatic agent, in its phenol form, based on the weight of the fiber-forming polymer. Each of the tows were removed from the individual impregnating solutions and separately immersed in individual aqueous solutions containing about 5 weight percent of hydrochloric acid, for periods sufiicient to convert the sodium salts to the free phenol. Each of the tows were then rinsed briefly in tap water and dried over night under normal room tempera- 'tures.

The dried, impregnated tows were individually immersed in an aqueous bath containing 0.1 weight percent of Igepon T (sodium n-methyl-n-oleyl taurate) and heated with stirring at 95 C. for a period of about 0.5 hour. The tows were then rinsed with tap water and dried over night at normal room temperatures.

Each of the dried filament tows were separately placed on the surmace of a nutrient agar seeded with Staphylococcus aureus contained on the surface of a hardened agar media plate, and subsequently incubated for a period of about 48 hours at a temperature between about 30 C. and 37 C. A zone of inhibition was observed around the test specimens containing 2,3,4,6-tetrachlorophenol, or pentachlorophenol, whereas an untreated test specimen did not provide the indicated zone of inhibition.

Similar good results are obtained using any concentration between about 0.5 weight percent to 20 weight percent based on the weight of the fiber-forming polymer of the bacteriostatic agents of the present invention.

Additionally, similar good result are obtained when the prescribed amounts of the bacteriostatic agents defined herein are incorporated in a finally shaped, irreversibly dried fiber from an aqueous solution as described herein.

It has also been found that similar good results are obtained when the prescribed amounts of the bacteriostatic agents defined herein are added directly to the aqueous polymeric saline spinning solution prior to formation of the finally shaped article subsequently produced therefrom.

Similar good results are also obtained when fiber and film-forming acrylonitrile polymers containing at least weight percent of polymerized acrylonitrile and up to 15 weight percent of one or more of such copolymeriZ- able materials as vinyl chloride, vinyl acetate, methyl and other alkyl acrylates or methacrylates, the vinyl pyridines, allyl alcohol and many others Well known to those skilled in the art are admixed with the prescribed amounts of the bacteriostatic agents described herein.

What is claimed is:

1. Composition of matter, the essential constituents of which are (1) a fiber-forming acrylonitrile polymer which polymer contains in the polymer molecule at least about 85 weight percent of acrylonitrile, the balance being another monoethylenica'lly unsaturated monomer that is compatible with acrylonitrile and (2) at least about 0.5 weight percent based on the weight of said fiber-forming polymer of a phenol selected from the group consisting of 2,3,4,6-tetrachlorophenol and pentachlorophenol.

2. The composition of claim 1, wherein the phenol is present in amounts between about 0.5 and 20 weight percent based on the weight of said fiber-forming polymer.

3. The composition of claim 1, wherein said fiberforming polymer is polyacrylonitrile.

4. A polymeric article of manufacture having bacteriostatic properties, said article capable of lying substantially in a single plane, having at least one major dimension, and at least one minor dimension less than about 0.1 inch, comprised of (1) a fiber-forming acrylonitrile polymer which contains in the polymer molecule at least about 85 weight percent of acrylonitrile, the balance being another monoethylenically unsaturated monomeric material that is copolymerizable with acrylonitrile and (2) dispersed therein at least about 0.5 weight percent, based on the Weight of the fiber-forming polymer of a phenol selected from the group consisting of 2,3,4,6- tetrachlorophenol and pentachlorophenol.

5. The article of claim 4 wherein the phenol is pres.-

References Cited by the Examiner UNITED STATES PATENTS 12/51 Seymour 16742 2/52 Rothrock 260-33.4

Lutz et a1. 16742 L211 167-42 Dubin et a1 16742 Mogensen et a1 8-4155 Genth 16742 JULIAN S. LEVITT, Primary Examiner.

LEWIS GOTTS, Examiner. 

1. COMPOSITION OF MATTER, THE ESSENTIAL CONSTITUENTS OF WHICH ARE (1) A FIBER-FORMING ACRYLONITRILE POLYMER WHICH POLYMER CONTAINS IN THE POLYMER MOLECULE AT LEAST ABOUT 85 WEIGHT PERCENT OF ACRYLONITRILE, THE BALANCE BEING ANOTHER MONOETHYLENICALLY UNSATURATED MONOMER THAT IS COMPATIBLE WITH ACRYLONITRILE AND (2) AT LEAST ABOUT 0.5 WEIGHT PERCENT BASED ON THE WEIGHT OF SAID FIBER-FORMING POLYMER OF A PHENOL SELECTED FROM THE GROUP CONSISTING OF 2,3,4,6-TETRACHLOROPHENOL AND PENTACHLOROPHENOL. 